The goal of this KOS application is provide the essential skills and experience that will allow the Principal Investigator to become a successful, independent physician-scientist. This proposal seeks to define a role for cyclooxygenase 2 (C0X2) in the pathophysiology and treatment of acute lung injury (ALI). ALI is a devastating clinical syndrome that affects more than 200,000 patients per year, with a mortality of 30-50%. Although a mainstay of therapy for ALI, mechanical ventilation, especially with high tidal volumes, can worsen existing injury or even cause de novo lung injury, a phenomenon referred to as ventilator induced lung inury (VILI). C0X2 is an inducible enzyme known to be involved in acute inflammation and increased vascular permeability. However, little is known about the expression of C0X2 in response to mechanical stress and its involvement in mechanical stress-induced lung injury. Preliminary data generated by the Principal Investigator have identified C0X2 as a candidate gene in VILI, demonstrating increased expression of C0X2 associated with increased lung inflammation and vascular barrier disruption in response to high tidal volume mechanical ventilation. Additionally, pharmacologic inhibition of C0X2 is protective, decreasing acute inflammation and enhanced permeability. We hypothesize that C0X2 expression is induced in response to high tidal volume mechanical ventilation and plays an important role in the acute inflammation and endothelial barrier disruption that accompanies VILI. We additionally hypothesize that the administration of selective C0X2 inhibitors may attenuate or prevent VILI. The Principal Investigator proposes to explore the precise mechanisms of action of C0X2 in mechanical stress-induced lung injury, using both in vivo and in vitro models. In SA #1, we will characterize the role of C0X2 in a well established, murine model of VILI correlating C0X2 expression and prostanoid production with biochemical and histologic indices of injury and exploring the regulation of 00X2 in response to mechanical stress. SA #2 will focus on cyclic stretch, a unique in vitro model of mechanical stress-induced lung injury. Using measures of endothelial resistance, immunohistochemistry, protein biochemistry, sIRNA, real time/RT-POR, and Western blotting, we will define the role of 00X2 in cyclic stress-induced cytoskeletal reorganization. In SA #3, define the efficacy of local and systemic 00X2 inhibition in VILI, using pharmacologic inhibition and gene silencing techniques. RELEVANCE (See instructions);Acute lung injury (ALI) is a devastating syndrome that kills more than 74,000 patients each year in the US and has very few therapeutic options. Mechanical ventilation is required for patients with ALI, however can itself cause or worsen lung injury. Research into the effect of mechanical stress on lung from ventilation are necessary to better understand this syndrome and to develop new treatments. (End of Abstract)